The invention relates generally to Langmuir troughs which are used to deposit monomolecular layers of fatty acids and the like on substrates, and deals more particularly with a barrier mechanism for isolating a drive chain from an active chamber in such a Langmuir trough to prevent contamination of the active chamber.
A basic procedure for the deposition of a monomolecular layer of fatty acid on a substrate was originally developed by Dr. Irving Langmuir. According to this procedure, a monomolecular layer was spread on the surface of water in a trough, and then compressed by a movable barrier supported at the height of the layer. This movement of the barrier also aligned the molecules such that a hydrophilic end of each molecule was oriented adjacent to the water surface and a hydrophobic end of each molecule was oriented above and out of the water. Then, a substrate, typically positioned in a vertical plane, was lowered into the water through the monomolecular layer and, in the process thereof, coated with the monomolecular layer. If this process was repeated, or if the substrate was subsequently raised out of the water through the monomolecular layer, another layer was deposited on the substrate over the first layer. Alternately, the substrate could initially be positioned in the water before the monomolecular layer was spread on the water's surface, and then the substrate raised out of the water to deposit a single monomolecular layer on the substrate.
The coated substrates have various applications. For example, if the substrate is a semi-conductor wafer and the molecules are cross linkable upon exposure to ultraviolet light, the monomolecular layer or layers on the wafer can be hardened by exposure to ultraviolet light and used to form masks to define an etching pattern on the wafer. In another application, the monomolecular layer or layers can be hardened and to form a dielectric of precise thickness in electronic components. In still another application, multilayer films having nonlinear optical properties can be obtained by appropriate alternation or other sequencing of films having an optically active chromophore and another film that does not. Multilayers of this type may possess second harmonic generation properties.
It was also previously known to provide a Langmuir trough divided into two active chambers by a lock, and to deposit layers of different molecules on the surface of water in each chamber. Then, the molecules on the surface of the water in each chamber were compressed, and a substrate lowered into one chamber, moved laterally beneath the water surface through the lock into the other chamber, and then raised out of this other chamber. The result was the deposition of two different or alternating layers on the substrate.
It was also previously known to divide a Langmuir trough into two active chambers by a fixed central barrier supported at the surface of the water in the chambers. A monomolecular layer of one type was deposited on the surface of the water in one chamber and a monomolecular layer of another type was deposited on the surface of the water in the other chamber, and both layers were compressed. A chain driven substrate was then circulated downwardly into one chamber through the respective monomolecular layer, arcuately passed underneath the central barrier, and finally passed upwardly through the other chamber and the other monomolecular layer to provide two alternate monomolecular layers on the substrate. However, a potential problem has developed in this technique because the chain can possibly transport molecules of one type from one chamber into the other chamber and thereby contaminate the other chamber.
Accordingly, a general object of the present invention is to provide a barrier mechanism to isolate the drive chain in the aforesaid system from one or both of the chambers to prevent molecules of one type from one chamber from being carried by the chain into the other chamber.
Another general object of the present invention is to provide a barrier mechanism to isolate a drive chain or the like from an active chamber in other types of Langmuir troughs.
Another, more specific object of the present invention is to provide a barrier mechanism of the foregoing type which does not interfere with the movement of the substrate or the associated chain.